Separation of wax constituents and the like from oil



Dec. 1, 1953 w. E. sKELToN ETAL 2,661,317

SEPARATION OF WAX CONSTITUENTS AND THE LIKE FROM OIL Filed March 17,1949 Patented Dec. 1, 1953 UNITED STATES .'ATENT OFFICE SEPARATION F WAX4CONSTITUENIS AND THE LIKE FROM IOIL Delaware Application March 17,1949, Serial No. 81,926

1 Claim. l

This invention relates to a continuous process for separation ofwax-like constituents from oil such as contained in hydrocarbon mixturesby treatment with an organic agent such as urea.

The invention concerns a continuous process for separation of wax andWax-like constituents from oil by treatment with an organic complexingagent having the structure:

where X may be either oxygen or sulfur. Examples of effective compoundsare urea, thiourea, and certain derivatives thereof which are capable offorming with waxy constituents of mineral oil solid crystalline complexcompounds readily separable from the oil.

More specifically, the present invention involves subjecting thecrystalline complex to treatment with a solvent liquid such as benzoland its homologs or a petroleum naphtha at an elevated temperaturesunicient to decompose the complex with a solution of the waxycomponents of the complex in the solvent, leaving the complexing agentin solid particle form. Advantageously, the resulting mixture issubjected to ltration thereby obtaining a iilter cake comprisingrecovered complexing agent in solid particle form. -The filter cakematerial is then recycled into contact with fresh feed oiladvantageously -in the presence of a polar solvent liquid such asvProcess for Separation of Wax-like Constituents From Oil, the aforesaidcomplexing agents such .as urea are useful in effecting separationbetween wax and normally liquid constituents of wax- `bearing mineraloil. In the case of separating wax; kfrom mineral oil ythe resultingcrystalline vabout 125 F. and may be decomposed by heating totemperature in the range about 150 to 180 F.

or higher in the presence of a wax solvent.

The invention of the present application is 2 particularly concernedwith the treatment of the resulting crystalline complex so as to recoverthe wax and also recover the complexing agent in a form particularlyuseful for recycling into contact with the fresh feed oil stream. Theinvention involves the discovery that the crystalline complex of wax andcomplexing agent such, as urea may be treated with an aromatichydrocarbon such as benzol, toluol, etc. or a petroleum fraction such asnaphtha at elevated temperature and thereby liberate the wax as asolution in hydrocarbon solvent While leaving the complexing agent incrystalline form and, therefore, in a condition particularly suitablefor recycling to the process.

Reference will now be made to the accompanying drawing wherein theprocess will be described with reference to the treatment of alubricating oil distillate having a Saybclt Universal viscosity of about300 seconds at 100 F. containing about 1% wax by volume and having aFreon haze test above minus 20 F. This haze test is determined by mixingthe oil with Freon (dichloro difiuoro methane) in the proportion ofabout Freon and 10% oil by volume, chilling the mixture and observingthe point at which Wax haze appears.

Feed oil is conducted from a source not shown through a pipe I to amixer 2 wherein it is brought into contact with urea in solidcrystalline form, the urea being introduced to the mixer from a pipe 3to which reference will be made later.

Alcohol, such as ethyl alcohol, is conducted into the mixer from a pipe5 and to which reference will be made later.

The urea is added through pipe 3 in an amount equal to about 3 to 8pounds of urea per pound of wax in the feed oil. The alcohol present inthe mixer may be 0.1% to 20% by volume of the feed oil.

The mixing is eiiected at a temperature about ,100 F., or in the rangeabout 75 to 125 F. and

as a result wax constituents of the oil enter into complex formationwith the urea forming a crystalline complex.

The resulting mixture of the oil and alcohol and complex and excess ureais conducted through pipe I0 to a lter Il, advantageously of thecontinuous rotary drum-type operated under pressure. In any case, thefilter apparatus is of conventional structure such as disclosed, forexample, in U. S. Patent 2,449,902 granted to Wynkoop Kiersted.

Filtration is effected at the aforesaid tem- -of urea crystals suspendedin alcohol.

per molecule.

perature thereby obtaining a lter cake comprising crystalline complexand excess urea and a filtrate of oil substantially free from anyundesired wax constituents. This filtrate is discharged through pipe I2to a solvent recovery unit I3 indicated in broken lines wherein solventalcohol is recovered from the oil. Since the oil may retain smallresidual amounts of urea, provision may be included in unit I3 forrecovering this residual urea by washing with alcohol or by other means.

The filter cake may be washed in situ in the filter in the conventionalmanner to Wash out retained mother liquor. This wash filtrate may becommingled with the main filtrate stream o1' may be separately treated.

The resulting washed filter cake is discharged from the filter andconducted through line by means of a conveyor to a mixer'2I wherein itis brought into contact with benzol or toluol or naphtha fractionintroduced from pipe 22. The contact with the hydrocarbon is effected at-an elevated temperature in the range 150 up to 200 F. or higher andsuch that the complex breaks down with liberation of the wax as asolution in the hydrocarbon and leaving urea in -crystalline form.

A heating coil may be provided in the mixer as indicated or other meansmay be provided for supplying the necessary heat.

The resulting mixture is removed from the mixer through pipe to a secondfilter 26 Wherein it is subjected to filtration so as to obtain a iiltercake consisting essentially of urea crystals. This lter cake may also besubjected to Washing with solvent liquid in situ and before dischargefrom the filter.

The resulting cake is removed through pipe 21 While the resultingfiltrate containing wax dissolved in benzol is discharged through pipe28 to a stripper 29.

In the stripper 29 the solvent liquid is stripped from the wax, the waxbeing discharged through pipe 30.

The aromatic hydrocarbon distillate is removed through pipe `3|condensed in cooler 32 and then conducted into pipe 22 previouslyreferred to. Additional aromatic solvent may be supplied throughpipe 33to compensate for losses in this operation.

While not shown, provision may also be made vfor recovering any residualsmall amounts of urea carried out in the filtrate from the filter 26.The filter cake discharged through pipe 21 may be returned by means of aconveyor to the mixer 2. f

While not shown, means may be provided for vaporization and recovery ofaromatic hydrocarjbons contained in the wax discharge from filter 26.`Advantageously, it is commingled with alcohol such as recovered in therecovery unit I3.

Thus, this recovered alcohol stream is conducted through pipe di)indicated in broken linesand added to the -lter cake, being dischargedfrom the filter 26 in amounts sufficient to form a slurry The resultingslurry is then conducted through pipe 4I communicating with pipe 3previously referred to and thereby being recycled to the mixer 2.

The dewaxed oil product discharged from the Irecovery unit through pipe43 will have a Freon haze of about minus 65 to minus 75 F.

In practice, it is advantageous to employ in the complexing zone, a lowmolecular Weight aliphatic alcohol having 1 to 5 carbon atoms Otherpolar solvent liquids may lremoving it by washing or stripping prior topassage to mixer 2 I. For example, the cake from filter II can besubjected to countercurrent contact with flue gas at about to 140 F. toevaporate the alcohol from the cake. The eifluent gas stream can then becooled and compressed to knock out the alcohol before recycling forreuse.

While mention has been made of applying the process to the treatment oflow viscosity oil nevertheless it is contemplated that the process maybe applied to the treatment of heavier oils and oils containing largeramounts of wax. It is contemplated that relatively viscous oils may bediluted With a low molecular weight petroleum hydrocarbon such aspentane, hexane or mixtures thereof or other naphtha hydrocarbons. Theprocess may be carried out under sufficient pressure to permit the useof liquefied normally gaseous petroleum hydrocarbons as diluents.

The process of this invention is useful in the treatment of other oilsand it is contemplated that it may be applied to the treatment of oilsderived from non-mineral sources, such as from animal, vegetable andmarine oils. It may be used for the separation of other than waxconstituents, for example, urea enters into complex formation withoxygenated hydrocarbons and either aromatic or naphthenic-typehydrocarbons having relatively long aliphatic side chains. Thus, theprocess may be used to remove other undesired constituents from oils ofvarious types such as gas oils for the manufacture of diesel fuels, jetfuels, etc.

The invention may have application in conjunction With conventional lowtemperature dewaxing operations veither to effect preliminary removal ofcertain Wax constituents prior to conventional dewaxing or to theremoval of residual wax constituents from oil previously dewaxed at lowtemperatures.

While urea has -been specifically mentioned, other substitutedderivatives thereof such as ethanol urea, diethyl urea, butyl urea maybe -composed of wax constituents and urea, separating by ltrationresulting complex from de- Waxed oil and polar solvent, recovering polarsolvent liquid from the dewaxed oil, subjecting s separated complex tocontact with benzol at a temperature in the range of about 150 to 200F., thereby decomposing said complex to form a mixture comprising asolution of wax in benzol and urea in solid particle form, filteringsaid last mentioned mixture to separate therefrom a substantiallyWax-free filter cake of urea in solid particle form and retaining somebenzol, commingling said cake retaining benzol with aforesaid recoveredpolar solvent liquid, and recycling' said commingled mixture intoContact with fresh feed oil.

WILLIAM E. SKELTON. HOWARD V. HESS. GEORGE B. ARNOLD. BOYD L. MAHAN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date i I, 1,830,859 Schotte et al Nov. 10, 1931 d 2,248,668 GeeJuly s, 1941 2,499,820 Fetterly Mar. 7, 1950 2,546,328 Arabian et alMar. 27, 1951 OTHER REFERENCES m Technical O11 Mission, Reel 143.Translation by Shell Development Co., of German application Bl90,197(BengemLpages 2-6, May 22, 1946 (included in Index released May 31,1946, pages 15 2-6 inclusive only).

